[sdiy] D-70 red goo of death - now parting out a D-70

[Dave Brown]

I repaired all the keys that the weights had fallen out of with the method
described below.  The remainder of the keys I was thinking of just
containing it but wanted to verify I could repair the flex circuits.

To remind you of the status, the flex key sense boards have fingers that
align with a flex interconnect.  When they separated all the fingers on the
flex interconnect stuck to the flex key sense board and were torn off.  I
repaired the missing fingers on both flex boards using the MG silver pen.
It was a reasonable price but it only worked the first time.  Then the pen
wicking mechanism dried up (like I expected it would) after first use and no
longer would flow silver.  I bought a small jar, cut open the pen, and just
emptied the silver into it.  I masked all the contacts and painted the
silver on with a small brush.  Peeling up the tape left very well defined
fingers.  I used an ohm meter to verify they all had continuity with the
runs.  I did the same on the mating flex interconnect. The fingers just lay
on top of each other with a small plastic backing piece so I was concerned
they might not all make reliable contact.  I lined them up and used tape to
hold the alignment and then folded the flex interconnect back.  I used a
toothpick and put a small drop on each of the new fingers then folded the
flex interconnect back and put the two push plugs that hold the plastic
across the top.  I know each finger made good contact as my silver drops
spread slightly and connected each pair of fingers.

You have to disassemble the entire synth except for the power supply and LCD
front panel to get the keyboard in or out.  The net of it is not one of the
keys operates.  Something is significantly wrong, but you can't really
access anything to scope the signals the way this synth is built.
Everything operates by MIDI just not by the keyboard.  I didn't want to
finish the keys until I knew the keyboard would operate so only about an
octave of keys are repaired.

I'm going to part this one out as I have invested enough time and energy and
it isn't that great of a synth.  Let me know if you need any D-70 parts,
boards, or modules except for the keyboard flex circuits. This synth just
wasn't designed to be long term reliable with that flex circuit interconnect
system.  I hate to give up but enough is enough.

Dave

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Bob Weigel
Sent: Monday, January 28, 2013 7:37 PM
To: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] D-70 red goo of death - not epoxy, maybe polyurethane

On 1/28/2013 6:13 PM, Dave Brown wrote:
> I heated up some water in a glass jar in the microwave (I'll have to get a
junk pan to do this in).  I went up to about 150 degrees F.  It 
> softens the goo enough that you can scrape most of it out.  If there was a
weight still in the key, then you can pry it out with a small 
> screwdriver.  Then you can dunk the key again and soften the goo and
scrape the rest out.
>
> The metal weights are a mess but I can put them in a pan and boil them.  I
think that will work pretty good.  I will have to have a 
> second pan because they are so sticky you can't set them down on anything.
>
> I'm still left with a film all over the inside of the key.  I tried
reheating it and then using a Q tip but the cotton just sticks to the 
> remaining goo.  Just for fun I poured some baking soda into the water and
it reacted and I got some crud floating on top.  I immersed the 
> key in again and used the Q tip and I could clean the key out really well.
It isn't perfectly clean, but clean enough that nothing will 
> ever drip out and it looks fine.
>
> I tried gluing one weight in using silicone.  I think that will work
nicely. The issue is I have to do this 60 more times!    I think the film
floating
> on the water will preclude doing more than a few keys before I have to
change the water.  It stays hot enough long enough that I think I can 
> just use the microwave to heat it up.
>
> I still need some tips on silver / carbon paint.  I can find some silver
epoxy, but I am not sure I want that.  I'm thinking of 
> something I can mask and then paint back on.  I did find these at Mouser
but Ouch at the price.
>
> 590-8420-P Chemicals SILVER CONDUCTIVE PEN 0.3 oz $23.01 590-842-20G
Chemicals SILVER PRINT 20G ( 3/4 oz) LIQUID $45.02
>
> Dave
>
> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl
> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Dave Brown
> Sent: Monday, January 28, 2013 3:25 PM
> To: 'Bob Weigel'; synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] D-70 red goo of death - not epoxy, maybe 
> polyurethane
>
> I think I agree with this.  The synth isn't worth the hassle of dealing
with harsh chemicals and possible accidents.  The goo does 
> soften at fairly low temperatures.  I found I could get it off the flex
circuit board by heating it up with my hot air gun, scraping the 
> excess off, and then cleaning it up with a Q tip and lacquer thinner.
Lacquer thinner tends to dissolve the goo when it is more fluid when hot.
>
> I think heating the keys in water may be a good way to go.  With the hot
air gun I can soften and scrape the stuff out of a key where they 
> weight has fallen out.  With those keys with the weights still in them I
don't think this would work very good.  The issue with heating in 
> water will be to make sure the soften goo doesn't get all over the keys.
>
> So, I am now left with how to repair the flex circuit boards.  There are
two small sections where the traces are damaged.  I assume these 
> are a thick film paint so I probably need something to paint over them.
They look like possibly silver-based.
>
> At the edge connectors the silver traces went to the edge (and are no
missing) and then had a thicker coating over them to form the actual 
> contact.  I assume I would want to paint down a silver higher conductivity
paint and then layer over that a thicker carbon/black coating.
>
> I haven't looked yet for conductive paints.  Any suggestions for a high
and medium conductivity paint?
>
> Dave
>
> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl
> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Bob Weigel
> Sent: Monday, January 28, 2013 2:49 PM
> To: synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] D-70 red goo of death - not epoxy, maybe 
> polyurethane
>
> I've usually just peeled the stuff off of keys when it gets away but  I've
never had to clean up the whole mess...but seems to me you could 
> just put it in hot water that isn't hot enough to deform the keys.  This
stuff melts at around 110 degrees F or so I think since it melts 
> in the air at temps near that.  Don't boil it for sure, that warps the
keys. I've heard of people doing that.  lol.  But when you get it warmed up 
> the weight should come out and clean all the adhesive gel off with a
scrubber or whatever and that should be the easiest I'd think.